Method of mixing resins with other material



Patented June 2, 1936 UNITED STATES PATENT OFFICE METHOD OF MIXING RESINS WITH OTHER MATERIAL No Drawing. Application May 29, 1930,

Serial No. 457,504

7 Claims. (c1. roe-+22) The present invention relates to a method of mixing resins such as Bakelite and similar compounds with finely shredded, powdered or granular material, either conductors or non-conductors.

N on-conductors may include wood flour, asbestos powder, shredded asbestos and shredded rags. Conductors may include graphite, coke and metal powders such as used for example in the manufacture of brushes for electric machines.

0' It is the object of the invention to devise a method of mixing resins and such materials as above referred to, which will be effective to secure a more intimate and homogeneous mixture of these materials in which the various ingredients which constitute such mixture are more uniformly distributed than has been heretofore possible.

The methods heretofore employed the mixing of resins with powdered or granular material, such for instance as the graphite or copper powder used in the manufacture of brushes, have been principally two. According to the first of these, the resin and other materials which are used in forming the article are pulverized and are mixed in powdered form, in any suitable mixing device,

while dry. In carrying out the second method, the

resin is dissolved in a volatile solvent such as benzol or alcohol or a mixture of the two. In this dissolved state, it is mixed with the other materials comprising the desired mixture, these materials being in powdered form. The solution is then evaporated in any suitable way to eliminate the volatile solvent and the residue is then adapted to be molded or dried in any desired manner.

The first of the methods above referred to is not altogether satisfactory because it is exceedingly difiicultto secure a homogeneous mixture of the various ingredients which goes to make up the whole. In some parts of the mass certain of the ingredients will be found in greater proportions than in other parts and if powdered metal is used in the mixture as in the formation of a brush, it will be found that it is unevenly distributed throughout the mass, and the conductivity of the brushes will not be uniform because of the unequal distributed copper particles. Therefore, because the first described method of mixing the various materials together is not altogether effective, it is found that a non-uniform product will 50 be the result, whether it be a brush or some other element made from the mixture of materials.

The second method described is somewhat more effective to secure a uniform and intimate mixture of the various ingredients, but because of the use of the volatile solvent for the binder the danger from fire is great and theprocess expensive because the solvent is not recovered. According to the present invention, a method is devised which is effective to secure a uniform mixture and eliminates the fire hazard, while it is also much less expensive because it eliminates the loss incurred by evaporation of the volatile solvent.

According to this invention, the materials which are being mixed are wet with lime water or some other alkali such as sodium or potassium hydroxide during the mixing process. Specifically, finely powdered graphite and finely powdered resin, such as powdered Bakelite, are placed in any suitable mixing machine and the lime water, or some other alkaline solution, such as sodium hydrate, sodium silicate or sodium carbonate is added slowly as the materials are mixed, until the mass in the mixing machine becomes a thick paste. The effect of the alkaline solution is to soften the particles of the resin on the surface thereof sufficiently to cause them to form an mtimate mixture with the graphite.

The quantities of the materials employed will vary to some extent with the alkali employed, but if lime water is used, a suitable mixture for forming brushes is obtained from the following quantities of the various materials used: eighty-eight parts graphite, ten parts Bakelite and two parts lime, by weight. 7

It will be noted that the addition of lime water is not sufiicient to cause the resin particles to be taken up in the solution, but since the lime water tends to dissolve the particles, the exterior thereof is softened. This causes a very intimate adhesion to take place between the various resin particles and graphite particles in the mixture. Any of the various alkaline solutions, such as above referred to, may be usedinstead of lime water with satisfactory results.

After addition of the lime water, the mixture may be washed, filtered and dried in any suitable way. The dried mixture may then be used in the manufacture of brushes or for any other purpose desired.

Also, instead of employing lime water to soften the Bakelite. the invention contemplates the use of calcium oxide and plain water to effect the same result. When calcium oxide is employed, the proportions which have been found to give good results in the formation of a brush for an electric machine are eighty-eight pounds graphite, ten pounds resin and two pounds of calcium oxide. It will be understood of course that if the materials are being mixed for use in the formation of difierent articles, the proportions of the various materials may not be the same. In carrying out the method, the calcium oxide is added as a powder to'the powdered graphite and resin during the mixing of the latter and all three are then: mixediinthe mixingimachine while water is added slowly until a thick paste is formed of substantially the same consistency as the paste secured when employing lime water. The action of the calcium oxide withwateris substantially the same as when lime water is used, the water and oxide forming calcium hydroxide during the process of mixing the mass. Subsequent to this operation the mixture may be filtered, washed and dried as above set forth. As'hasbeenpointe'd out, the advantages of this method of mixing resins and other materials aresapparent. i-Azbetter mixture is secured than with methods formerly used, the method is less expensivelthanhthat in which the resin is dissolved in a volatile solvent, and a better :eand-imore uniform product may, therefore, :tbe QbtainedEat" aalowerxcost: than with formerumethods.

While the vform .of embodiment of i the present invention as herein disclosed, 'tc'onstitutes avpreferred form, itis .to'be understood :that other forms might be adopted, tall rooming zwithin the scope oftheiclaims which follow.

What 'is'iclaimed is 1 as follows:

1. ThQpDl'OCESS Ol mlXlHglESlIlSCWllIlLglflIllIlEl' or powdered mdtellalSWhlOhiOOllSlStSlnf'mlxing dry f powdered :resin with some other dry Dowdered material, adding :a quantity of -alkaline solution during the llllXlilQ'ODGllitlilOIiSllfilclelltiil soften the surface of the psrticlesini resinsbut insuilicient to .diss olve Issid particles, lllaShlllg "iit iit tilt t l Illlm tits lbw; /z

sufiicient to dissolve the resin, washing and filtering the paste and drying the washed residue.

3. The process of mixing resins with granular or powdered materials which includes the steps of mixing dry powdered resin with other dry pow- 5 dere'd materials and adding a quantity of alkaline solution duringthe mixing-operation sufficient to cause the resin to become sticky but insufficient s'to-z dissolve the resin.

4. The method of .mixing materials for formingnbrushes for electric machines which includes the steps of mixing substantially eighty-eight :parts powdered graphite with substantially ten parts Bakelite powder, and adding two parts "limein the form of lime water during the mixing operation.

s5. The-zprocesstof mixing resins with granular ".oripowdered materials which consists in mixing powderedresin, calcium oxide powder and other powdered or granular material, adding avquantity-of water iduring the'mixing operation sufficient tosreact l-with the:.calcium oxide andsoften the'rresin :but insufiicient to dissolve the resin, washing and iflltering sthe mixture and driving the residue.

165 Thermethod of mixing resins with granular .or .powdercd;materia1s :which includes the steps of :tmixing powdered i resin with other powdered materiala-i'andfiadding a quantity of calcium oxide and rvntorto such i mixture during the mixing eperation sufficient to softenthe resin but insuiiisient .toidissolve the resin.

* lj The niethod 0f 1 mixing a materials for "form- 'iHg'bI'UShGS iOI electric machines which includes the steps i of mixing substantially eighty-eight parts powdered rgrsphite, ten parts Bakelite it i 

